The objectives of the proposal are optimization of the prototype hand- held imaging camera developed in Phase I, including significant performance improvements and addition of automated image analysis techniques, and evaluation of the camera in clinical studies. The function of the camera is to image distributions of a radiolabeled colloid injected into cancer patients to localize the sentinel lymph node (SLN) in the drainage path of the primary tumor. SLN have been implicated in the spread of malignant cells so the pathology of the SLN is indicative of the spread of cancer. The spread of the colloid from injection can take one or many paths and it may remain close to the primary or travel to distant non-intuitive node basins. These ambiguities make SLN localization challenging and only a handful of experienced specialist are highly successful in SLN localization. The imaging probe developed under this project facilitates SLN localization. The probe can be used before and during surgery to trace the path of the colloid and identify the SLN. One innovation added to the device in Phase II will be automatic image analysis techniques that allow the user to rapidly scan over suspected regions and be notified when concentrations of colloid are detected by the camera. In this way the user is alerted to areas that should be imaged. The hand-held camera promises to reduce the mean surgical time to localize SLN, reduce the number of procedures required to obtain proficiency, increase confidence in SLN localization and minimize surgical intervention. Clinical studies will be conducted to evaluate the effectiveness and utility of the imaging device both preoperatively and intraoperatively. Nuclear medicine physicians inexperienced in SLN localization will evaluate use of the imaging probe presurgically, and SLN experienced surgeons will test the device intraoperatively. Feedback provided by the physicians will contribute to the Phase II optimization process. PROPOSED COMMERCIAL APPLICATIONS: This project will result in an imaging probe to greatly facilitate the localization of the Sentinel Lymph Node during the staging of melanoma and breast cancer, among other potential tumor types. The imaging probe offers great advantages over the currently employed non-imaging probes at the same cost. The dynamic field of Sentinel Node Scintigraphy is growing in acceptance and scope. Many hospitals routinely use Lymphoscintigraphy and could enhance the procedure with this probe. The imaging probe developed here, at no extra cost to wasting non- imaging probes, will provide physicians with a more functional instrument that can carry the Sentinel Node technique further and faster.